Just my 2 cents, as a contrabass tuba player. (Almost all tuba players in the US, and some other countries play the contrabass tuba in most orchestras and concert bands - the bass tuba is considered a specialty instrument for brass quintets or high solo passages in orchestral music -- in most of Europe the standard orchestral instrument is the Bass tuba in F). It looks like the SSB Contrabass tuba has 3 dynamic levels, naturally the softest layer has the longest notes and smoothest loops. I think it would make sense, and make the contrabass tuba more useable, if that lowest dynamic's loudness was raised and used to cover more of the mod wheel range, then let the MF and FF samples come in much closer to the top mod wheel range.
As for the question raised in this thread earlier about additional instruments, and where to go with expansions. (which I hope will be done). Piccolo trumpet, Flugelhorn, and Euphonium would be my list for additional instruments. (Maybe a Wagner tuba - they are somewhat common in film music, generally played by the horn players I think) Then as an expansion give us 2nd and 3rd trumpets, 2nd, 3rd, and 4th horns, and an additional tenor trombone.